The adsorption of zinc from aqueous solutions on cassava peels (Manihot esculenta) modified with citric acid was studied. Cassava peels were modified with citric acid according to a fractional experimental design with central point, which had as independent variables: mixing time, drying time, reaction time, mixing temperature, reaction temperature, and biomass/acid ratio. In order to determine the best conditions to perform the chemical modification, removal experiments were carried out with the samples specified in the experimental design. Under these conditions, kinetic experiments were developed resulting in fast adsorption of zinc with equilibrium times within 20-30 minutes range, and adsorption capacities of 3.042 mg/g and 4.904 mg/g for zinc solutions of 30 and 50 mg/L, respectively. At these initial concentrations of zinc, the experimental data fit the kinetic pseudo-second order model.